Hydraulic press for compression of powder

ABSTRACT

Hydraulic press for compression of powder having upper punch, lower punch and die; die and upper punch operated by pistons respectively in two cylinders, there being hydraulic conduit means interconnecting the two cylinders for operating the die moving piston in dependency upon upper punch movement. A valve is connected to the conduit means and controlls a hydraulic bleeder path. The valve is actuated by means connected to be responsive to the relative positions of the first and second pistons, to control the characteristics of that defining the dependency of die movement upon movement of the upper punch.

iJted' States Patent Hermes Sept. 11, 1973 HYDRAULIC PRESS FORCOMPRESSION OF POWDER [75] Inventor: Rolf Hermes, Rheydt-Giesenkirchen,

Germany [21] Appl. No.: 158,783

[30] Foreign Application Priority Data July 3, 1970 Germany P 20 33891.4

[56] References Cited UNITED STATES PATENTS 9/1948 Tucker 425/78==HEE=== v 3,647,332 3/1972 Schmaus 425/78 2,391,362 12/1945 2,882,5564/1959 3,172,182 3/1965 Assmann 425/78 Primary Examiner-J. Howard Flint,Jr. Attorney-Ra1f 1-1. Siegemund et a1.

[5 7] ABSTRACT Hydraulic press for compression of powder having upperpunch, lower punch and die; die and upper punch operated by pistonsrespectively in two cylinders, there being hydraulic conduit meansinterconnecting the two cylinders for operating the die moving piston independency upon upper punch movement. A valve is connected to theconduit means and controlls a hydraulic bleeder path. The valve isactuated by means connected to be responsive to the relative positionsof the first and second pistons, to control the characteristics of thatdefining the dependency of die movement upon movement of the upperpunch.

10 Claims, 1 Drawing Figure HYDRAULIC PRESS FOR COMPRESSION F POWDER Thepresent invention relates to a hydraulic press for compression of powderof the type wherein movement of press die or lower punch during anoperating stroke (for compression) is controlled in dependeny upondisplacement of the upper punch.

Hydraulic presses for compressing metal powder are well known. Amongthem constructions are known in which not only the upper punch or ram ismoved but also the die member itself, whereby the beginning of the diemovement is determined by appropriately positioned stops. The die movesonly during part of the compression stroke while in a subsequent phasethe press punch moves alone. A homogeneous metallurgical structure ofthe compressed blank cannot be ex pected by phasing the operation andproviding discontinuous movement of press elements in that manner.

Another hydraulic press is known wherein die and upper punch can moverelative to each other, butthe instant of beginning a die followermotion cannot be determined and prescribed with sufficient accuracy.Moreover, the relative speed of the die is also not'controllable withsufficient accuracy. Another known variety of hydraulic press forcompression of powder has hydraulically operated pistons connectedrespectively to upper punch and die; and the pressure in the pistoncylinders is controlled by suitably connected valves; there is providedan additional valve to branch off a particular amount of pressureliquid. The additional valve itself is not controlled, so that mutualdependeny of movement of punch and die is not guaranteed, and it is notcertain that the position relation remains accurate throughout theoperation, so that quality of the pressed work varies significantly.

The present invention, therefore, has a primary object to provide ahydraulic press for compression of metal powder which guarantees ahomogenic metallurgic structure of the pressed work or block. Inaccordance with the present invention, it is suggested to provide acontrolled valve to bleed or branch off part of the flow of controlliquid flowing between the cylinders in which run pistons forcontrolling the positions of upper punch and of lower punch or die. Thecontrolled valve is connected to an actuator, which responds to therelative disposition of these pistons for positively establishingpositional dependency. Particularly the valve may be carried by an armthat moves up and down with the die, while the valve actuator proper isparticularly linked to the upper punch. The relative positions of upperpunch and die determines the control state of the valve, which, in turn,determines the extent and effectiveness of bypass for thehydraulicconnection between the two hydraulic motors as controlling dieand punch displacement. The invention permits additionally adjustment ofthe relative position, e.g., between upper and lower punch from whichthere is to be dependency of movement. Also, the slope of the transitionbetween independency and dependency is determinable and adjustable. V

While the specification concludes with claims particularly pointing outand distinctly claiming the subject matter which is regarded as theinvention, itis believed that the invention, theobjects and features ofthe invention and further objects, features and advantages thereof willbe better understood from the following description taken in connectionwith the accompanying drawings in which:

The FIGURE illustrates somewhat schematically a flow diagram with somepertinent construction details for a hydraulic press control system inaccordance with the preferred embodiment of the present invention.

Proceeding to the detailed description of the drawings, there is shown apress die member 17, a lower press punch 18, and an upper press punch 19disposed in a housing, stand, frame, or the like, and denoted generallywith reference numeral 13. These are the elements for the hydraulicpowder press and they are not shown in great detail.

The upper press punch is connected to a piston 2 that runs in acylinder 1. The die 17 is connected to a piston 6 that runs in acylinder 4. Three valves I, II, III, control application of pressure andconnection of venting outlet to the piston chambers at opposite sides ofthe pistons. A hydraulic pump H provides pressure fluid into the variousconduits and is driven by a suitable motor M. Additionally valves I andII govern a path 31 that includes a check valve 32 between the twopiston chambers.

The two pistons are stepped so that the respective opposite surfaces ofthe two pistons are of different dimensions. Consequently, there is anannular chamber 3 in cylinder 1, which is connected via valves I and IIand check valve 32 to an annular chamber 4 in cylinder 5. The twoannular chambers are, thus, particularly established adjacent thesmaller surfaces of the respective pistons 2 and 6. The lower punch 18is stationary in housing 13.

Up to this point, the arrangement is substantially known per se. Thevalves I, II, III, are appropriately controlled, whereby particularlypiston 4 may be moved in dependency upon movement of piston 2 during anoperating stroke, and pressure fluid, displaced from chamber 3, isforced into chamber 4, whereupon die 17 moves down as punch 19 movesdown.

For retraction and press opening, each piston is independentlydisplaceable so as to retract lower punch 18 (through lifting of die 17)from upper punch 19 through lifting the latter. During this phase,annular chambers 3 and 4 are not in communication for transfer ofpressure fluid from one to theother. Hydraulic operation of a hydraulicpress does not require detailed description. However, such-a device isnot adequate. for controlling the motion of the die to the desireddegreeof dependency. For this, controlled bypass or bleeder or branch-off path33 is needed. I

In accordance with the preferred embodiment of the invention, piston 6is connected to an arm 10 on which is mounted a follower control valve 7which regulates branch or bleeder line 33 for discharging pressurizedliquid from connection 31 to venting outlet 34. The follower controlvalve 7 has two terminal operating positions, but permits gradualtransition from one to the other.

In the illustrated position, branch line 33 is directly connected toventing point 34. In the alternative position, line 33 is cut off andcompletely disconnected from venting outlet 34, so that the fluid, thendisplaced fromchamber 3, all flows into chamber 4. For inbetweenpositions of controlled valve 7, there is more or less strongthrottling, i.e., higher or lower fluid flow impedance is established,for controlling the amount of pressure fluid that is bled off conductorline 31 via conduit or line 33 accordingly.

Valve 7 is under control of an actuator 71. Due to disposition of valve7 itself on arm 10, this position is part of the actuation input andestablishes response thereof to the position of piston 6 and die 17. Theactuator displacement relative thereto introduces the disposition ofpiston 2 as contributing to the control of valve 7. For this, adjustablelinkage 20 is provided as connecting means.

Actuator 71 is connected to the free end of lever 8, having a pivotpoint 9 in an extension of arm 10. The lever 8 carries a feeler roll 21,mounted to lever 8 in between pivot point 9 and the arm end that carriesactuator 71. The vertical position of roll 21 on lever arm 8 can beadjusted by means of a spindle 16.

A bevel gear 22 links spindle 16 via an articulated drive to anadjusting knob 23 that is accessible from the outside of housing 13.Upon turning knob 23, the spindle turns and feeler roll 21 is lowered orlifted, depending upon the direction of turning knob 23.

Feeler 21 bears against'a lever 11, having a pivot point 12, journalledon a guide 14 which is affixed to housing 13. An externally accessibleadjusting knob 24 turns a spindle 25 and, thereupon, pivot 12 isadjusted in direction of double arrow 26, depending upon the directionof knob turning. This direction of pivot displacement is particularlycharacterized in that it takes place in direction transverse to thedirection of displacement of upper punch 19.

The free end of lever arm 11 is linked via a scanning or feeler roll 27with a straightedge 15 which is secured to piston 2 of upper punch 19 bymeans of suitable arm structure 28. straightedge 15 is orientedtransverse to the direction of motion of upper punch 19, so that roll 27can roll there along as indicated by arrow 26, but only upon adjustmentby knob 24.

The device as described operates as follows:

During powder press working piston 2 is moved in cylinder 1 in thathydraulic pump H, as driven by motor M, causes pressure fluid to flowinto the upper portion of chamber 1, above piston 2, to move the pistonand upper punch 19 in down direction. Pressure fluid that has beencontained in (i.e., previously pumped into) annular chamber 3, isdisplaced via the valves 1 and 11, conduit 31, and the uncontrolledcheck valve 32 therein, to enter the annular chamber 4, as describedabove. However, branch 33 bleeds some of the displaced pressure liquid,as valve 7 is fully or partially open, so that annular chamber 4 is, infact, not pressurized. As long as valve 7 is completely or partiallyopen, outlet 34 is fully or partially efi'ective on the end of bleederline 33.

The annular chamber 4 will be pressurized only if during down motion ofpiston 2 the controlled valve 7 is actuated via straightedge l5, lever11, feeler 21 and lever 8, for closing the controlled valve 7. Therefor,during the initial phases of compression, piston 6 remains stationaryand so does arm 10. This then delays down motion of piston 6 and die 17,even the onset of such down motion is delayed. However, as piston 2moves progressively down, straightedge 15, as engaging feeler 27, pivotslever 11 counterclockwise and feeler 21 is pushed down, so that actuator71 begins to throttle valve 7. The operation of the follower controlvalve causes throttling of the branched off pressure liquid, and aftersome time even a complete turn-off of the branch is established, so thatpressure builds up in chamber 4 from the fluid as displaced from chamber3, and piston 6 with die 17 begin to move down.

The die motion is controlled, so that the relation of speed of upperpunch 19 to speed of die 17 is determined by (and could be made equalto) the relation of total length of lever 11, as between pivot point 12,and the point of engagement of straightedge 15 by the feeler roll 27 tothe length as established between pivot point 12 and feeler 21.Significantly now, this latter ratio can actually be adjusted down to avalue of 1:1 by appropriate lateral positioning of the pivot point 12,shifting the feeler 27 directly into vertical alignment with feeler 21.

Lever 8 functions as an amplifier as to transmission of displacement andparticularly provides an increase of the control deflection as acting onthe actuator 71 of valve 7. The gain of that amplifier is given by therelation of the total length of lever 8 as between pivot point 9 andactuator valve 71, to the partial length as between pivot point 9 andthe disposition of feeler 21 on lever arm 8.

By means of adjustable spindle 16, the onset of the die motion can beadjusted. It should be noted that lever 11 may normally rest on feeler21, while upon complete retraction of piston 2, straightedge 15 does notnecessarily rest on feeler 27. The tap between them represents the delayof the onset of operation of valve 7. However, that delay can be reducedto zero by adjusting spindle 16 so as to lift feeler 21 (and lever 11)until feeler 27 engages straightedge 15 so that right from the beginningthere is effective coupling of punch 19 and its hydraulic drive, andvalve actuator 71.

Such adjustment will be necessary primarily in case a rather tall workis to be pressed. Furthermore, it can be seen that in the particularposition as adjusted by knob 24, there is a 1:1 transmission as betweendown displacement straightedge 15 and down displacement of actuator 71,after the straightedge 15 has engaged feeler 27. Upon displacing pivot12, e.g., to the right, feeler 27 is displaced accordingly and thetransmission ratio is larger, to obtain complete throttling by valve 7more quickly. It will be appreciated that manipulation of controls 23, 25, permits adjustment in the characteristics that defines the dependencyof die movement upon movement of the upper punch.

After valve 7 has closed, punch 6 moves down also, and the valve closingis dynamically maintained by mechanism 20. Finally, at the end of thepowder compression operation, the stepped pistons 2 and 6, as well asthe upper punch 19, and die 17 are subject to individual controloperation by valves 1, l1 and III. This way, they can be independentlyreturned to initial position. The linkage via the follower valve doesnot follow or track this return operation. The invention permits anexact and high accurate control of die movement using a combination ofhydraulic and mechanical adjustment devices and it was found that thatcombination ultimately results in a very uniform microstructure of thecompressed powder.

The invention is not limited to the embodiments described above but allchanges and modifications thereof not constituting departures from the'spirit and scope of the invention are inteded to be included.

I claim:

1. Hydraulic press for compression of powder having upper punch, lowerpunch and die, a first and second one of these three elements beingmovable relative to each other for press operation, the relative motionbeing provided by means of first and second pistons respectivelyconnected to these first and second elements and respectively moving infirst and second cylinders, there being hydraulic conduit meansinterconnecting the two cylinders, the improvement comprising:

a branch conduit means conductively connected to for tapping the saidconduit means and leading to a venting outlet; a valve means inserted inthe branch conduit means for opening, closing or throttling a hydraulicbleeder path from the conduit means to the venting outlet;

actuation means connected for operating the valve to obtain saidopening, closing or throttling of the valve means; and

connection means connected to be responsive to the relative positions ofthe first and second pistons, further connected to the actuation meansfor operating the actuation means in dependence upon a particularcharacteristic as between the relative positions during compression.

2. Hydraulic press as in claim 1, the connecting means comprising afirst lever; means for pivotally linking the first lever to the firstpiston, the first lever having an arm, the arm being linked to theactuation means; a second lever; means for pivotally linking the secondlever to a stationary part of the press and coupled to the first leverfor transmitting displacement motion thereto; and means connected to thesecond piston for pivoting the second lever.

3. Hydraulic press as in claim 2, the coupling of the first to thesecond lever being externally adjustable for determining the onset oftransmission of displacement motion by the first piston upon theactuator.

4. Hydraulic press as in claim 2, the pivot point of the second leveradjustable to be effective transverse to the direction of displacementof the upper punch upon the second lever as pivot motion thereof.

5. Hydraulic press as in claim 1, the second piston operating the dieand having an arm, the valve being mounted on said arm, the first pistonoperating the upper punch, the valve actuation; means being linked bythe connection means to the first piston.

6. Hydraulic press as in claim 5, the connection means comprising, afirst lever pivotally linked to said arm;

an adjustable feeler on the first lever;

a second lever pivotally linked to a stationary part of the press andengaging the feeler;

a second feeler on the second arm; and

means for engaging the second feeler and coupled to the first piston,for transmitting displacement of theupper punch to the second feeler forfurther transmission via the second arm, the first feeler, the firstlever, and the actuator.

7. Hydraulic press as in claim 6, the last means including astraightedge, displaced with the first piston in direction transverse toits extension, the pivot of the second lever adjustable in the directionof extension of the straightedge, to change the distance between thepoint of engagement of the second feeler and the straightedge, and thepivot of the second lever.

8. Hydraulic press as in claim 1, the connection means adjustable todetermine the onset of closing the valve in the bleeder path for timingthe beginning of dependent displacement of the die.

Q Hydraulic press as in claim 1, the connection means adjustable todetermine the slope of the transition between independency anddependency of relative movement of first and second pistons.

10. Hydraulic Press as in claim 1, the connecting means comprisingadjustable lever means respectively connecting the actuation means tothe first and second piston, the said particular characteristicproviding for venting through the value means so that the speeds of thepistons have a predetermined ratio as adjusted in the lever means.

1. Hydraulic press for compression of powder having upper punch, lowerpunch and die, a first and second one of these three elements beingmovable relative to each other for press operation, the relative motionbeing provided by means of first and second pistons respectivelyconnected to these first and second elements and respectively moving infirst and second cylinders, there being hydraulic conduit meansinterconnecting the two cylinders, the improvement comprising: a branchconduit means conductively connected to for tapping the said conduitmeans and leading to a venting outlet; a valve means inserted in thebranch conduit means for opening, closing or throttling a hydraulicbleeder path from the conduit means to the venting outlet; actuationmeans connected for operating the valve to obtain said opening, closingor throttling of the valve means; and connection means connected to beresponsive to the relative positions of the first and second pistons,further connected to the actuation means for operating the actuationmeans in dependence upon a particular characteristic as between therelative positions during comprEssion.
 2. Hydraulic press as in claim 1,the connecting means comprising a first lever; means for pivotallylinking the first lever to the first piston, the first lever having anarm, the arm being linked to the actuation means; a second lever; meansfor pivotally linking the second lever to a stationary part of the pressand coupled to the first lever for transmitting displacement motionthereto; and means connected to the second piston for pivoting thesecond lever.
 3. Hydraulic press as in claim 2, the coupling of thefirst to the second lever being externally adjustable for determiningthe onset of transmission of displacement motion by the first pistonupon the actuator.
 4. Hydraulic press as in claim 2, the pivot point ofthe second lever adjustable to be effective transverse to the directionof displacement of the upper punch upon the second lever as pivot motionthereof.
 5. Hydraulic press as in claim 1, the second piston operatingthe die and having an arm, the valve being mounted on said arm, thefirst piston operating the upper punch, the valve actuation; means beinglinked by the connection means to the first piston.
 6. Hydraulic pressas in claim 5, the connection means comprising, a first lever pivotallylinked to said arm; an adjustable feeler on the first lever; a secondlever pivotally linked to a stationary part of the press and engagingthe feeler; a second feeler on the second arm; and means for engagingthe second feeler and coupled to the first piston, for transmittingdisplacement of the upper punch to the second feeler for furthertransmission via the second arm, the first feeler, the first lever, andthe actuator.
 7. Hydraulic press as in claim 6, the last means includinga straightedge, displaced with the first piston in direction transverseto its extension, the pivot of the second lever adjustable in thedirection of extension of the straightedge, to change the distancebetween the point of engagement of the second feeler and thestraightedge, and the pivot of the second lever.
 8. Hydraulic press asin claim 1, the connection means adjustable to determine the onset ofclosing the valve in the bleeder path for timing the beginning ofdependent displacement of the die.
 9. Hydraulic press as in claim 1, theconnection means adjustable to determine the slope of the transitionbetween independency and dependency of relative movement of first andsecond pistons.
 10. Hydraulic Press as in claim 1, the connecting meanscomprising adjustable lever means respectively connecting the actuationmeans to the first and second piston, the said particular characteristicproviding for venting through the value means so that the speeds of thepistons have a predetermined ratio as adjusted in the lever means.